1. Field of the Invention
The present invention relates to an emphasize system for an electronic musical instrument and, more particularly, to an emphasize system which emphasizes a predetermined frequency range component of a musical tone.
2. Description of the Prior Art
As an electronic musical instrument which controls the output level of a predetermined frequency range component of a musical tone in accordance-with a tone volume, the following apparatus is known. That is, an instrument generates a waveform signal having a large number of harmonic components in a sound source circuit, and when this signal is filtered through a filter circuit to cut unnecessary harmonic components, a filter constant is changed in accordance with a musical tone level outputted from the sound source circuit, thereby controlling a harmonic component ratio (Japanese Patent Publication No. Sho 40-3589).
In another known apparatus, a tone volume level of a musical tone signal to be generated is detected, and characteristics of a tone color filter are changed on the basis of the detected level, thereby controlling a harmonic overtone component ratio in a musical tone signal (Japanese Patent Publication No. Sho 46-35590).
However, since either of the prior arts described above simply changes frequency characteristics of, e.g., a filter in accordance with a tone volume level of a musical tone, delicate and colorful changes in tone colors cannot be satisfactorily provided.
For example, when a musical tone having spectrum components concentrated in a low-frequency range is inputted, a conventional system undesirably amplifies a frequency range (high-frequency range) having no harmonic overtone components, resulting in a low S/N ratio.